Light brown smoke at WOT

[Falcon_LS]

I was merging on an empty highway this afternoon in the Merc, and just decided I'd take this opportunity to floor it, since it isn't common. It was in third gear at roughly 60 km/h (40 MPG) and downshifted to first after flooring.

Immediately after it downshifted, and acceleration picked up, I noticed a trail of what appeared to be light brown smoke in the rearview mirror. Seemed to be coming from both tailpipes. Although it went away, I kept it floored until it maxed out at 200 km/h (125 MPH). I drove for about 9 km (5.6 miles) and slowed back down, but when I repeated it (downshift into first from third), there was no smoke at all.

Any idea what may have caused the brownish smoke? Carbon built up in the combustion chambers I take it? Thanks!

 

[boxcartommie22]

just blowing out the carbon

 

[brentalan]

It means that you are running a bit rich, some unburned fuel blowing out the exhuast. All of my cars do this, but more so the carb'd cars.

 

[citationxeleven]

The Italian tuneup!

 

[NateDN10]

Originally Posted By: boxcartommie22
just blowing out the carbon

+1.

Doesn't necessarily indicate a problem, especially if you floor it infrequently.

 

[AdRock]

I had an old guy in the mid 90's that would bring his car to me at the shop about every 6 months so I could go blow all the junk out of it. He drove it like an 80 year old and was afraid to drive it like that.

 

[rslifkin]

Sounds like blowing out carbon buildup. My Jeep did the same thing during the first couple WOT runs after I got it (PO drove like a grandma most of the time).

The solution: run the engine hard more often.

 

[mechtech2]

Carbon from modern fuel is way different than old style leaded fuel deposits.
They used to accumulate rapidly, but blew out rapidly!
Modern deposits are hard and normally not sooty.
But all there is is fuel, deposits [engine or exhaust [converter]], and oil.
Fuel [rich] or depostis fit the bill.